Archive for September, 2011

Storm testing

Matt Travis, (R) and Ron Tatley prepare the Design Verification Test Chamber to hit the installed mock-up with the extreme conditions faced by the residence it represents.

Our Design Verification Testing of the mock-up from the leaky $6.6 million San Francisco home continued Wednesday with water- or “storm-” testing.

In this series, following procedures from ASTM E 331, Matt Travis, Design Verification Testing Specialist; Ron Tatley, inventor of the Design Verification Test Chamber; and Courtney Murdock, PROSOCO’s Director of Project Testing, ramped up the chamber from a simulated 25 mph wind-driven rain shower to a full-blown 150 mph — per the instructions of the architect who sent in the mock-up.

As I mentioned in yesterday’s post, litigation is involved in this investigation of the house’s failed building envelope. That’s why I’m not using names of the architect or the home-owner who hired the architect.

The mock-up featured everything found in the walls of the home itself, including stucco cladding, a window, building papers, and electrical- and air conditioning penetrations. The contractor who’s been hired to repair the house built the mock-up.

Matt and Ron installed the mock-up on the small side of the chamber. The stucco “outside” of the mock-up faces into the chamber where it gets “rained” on from the chamber’s spray racks. The mock-up’s plywood and wood stud side faces out.

If, or rather, when the water from the spray racks penetrates the exterior, you can plainly see it coming through the wood.

Courtney points out water coming through the wall during "storm" testing.

Wednesday’s test procedure called for 15 minutes of exposure to spray at increasing air pressures. The increased pressure corresponds to various wind speeds. In this test, Matt and Ron pumped air into the chamber to simulate 15 minutes exposure to rain at 25 mph, 33 mph, 70 mph, 100 mph, 125 mph and 150 mph.

During each 15-minute test, Matt, Ron and Courtney closely inspected the wall for water coming through.

After 15 minutes, they shut the machine down for five minutes. Then they fired it back up to the next-higher pressure/wind speed, as specified by E 331.

Each time they discover a leak, Ron and Matt investigate until they find the leak’s origin. Where it shows up on the plywood and stud side of the mock-up isn’t necessarily where it entered on the stucco side.

Each time they find a leak, Matt plugs it with PROSOCO R-GUARD Emergency Water Stop. The blue paste temporarily seals the leak while vividly marking the spot.

At just under 10 minutes of simulated 100 mph wind-driven rain, the latest water penetration shows up. It’s coming from an electrical box penetration about halfway up the wall. The penetration is flashed with a peel and stick on the exterior-facing side of the plywood, and there’s a flange over that, but none of the edges of the peel and stick or the flange were sealed to the wall.

In this test, water didn’t get in at lower pressures. At 100 mph, however, water goes up as well as down, and finds its way into all sorts of places you’d never guess it would. The house being investigated, it turns out, often faces 100 mph wind-driven rain.

This penetration was protected on the other side of the plywood by a peel and stick membrane topped by a flange that is part of the electrical box. Water came through after about nine minutes and change of simulated 100 mph wind-driven rain -- a condition that the home under investigation, high in the Bay Area hills, faces routinely.

That’s the lesson Design Verification Testing teaches. Water doesn’t always do what you think it will. Materials don’t always behave the way you think they will, especially when conditions turn extreme… and there are few places that don’t experience extreme weather, sometimes at least.

These leaks are actually pretty small, Ron says. The trouble is that they don’t stay that way. Each wetting causes successively more deterioration, especially if the wall can’t dry out — such as when it’s got an impermeable vapor barrier installed.

It isn’t a poorly built wall by typical standards, Ron said. It’s just that typical standards almost always let water in at some point. By building and testing for the specific conditions the structure will face, instead of “typical standards,” you can make sure you don’t find yourself in lawsuit-land, helping to feed the multi-billion dollar construction litigation industry — like the builder of the home we’re checking out now.

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Ron Tatley (L) and Courtney Murdock watch as Matt Travis ramps up the air pressure in the Design Verification Test Chamber to simulate a modest 25 mph wind speed.

Our Design Verification Test Chamber is seeing some action today. Here’s the story so far.

A $6.6 million residence in San Francisco overlooks the Golden Gate and San Rafael Bridges. The view from the stucco-clad home is breathtaking, says our man on the scene, PROSOCO manufacturer’s rep Tim Sinnott, Sinco Sales, Danville, Calif., but along with that you get 100 mph wind and wind-driven rain.

So the house is seeing air leakage and water intrusion.

The owner hired an architect to investigate where and how the leaks occur. There’s litigation involved, so I’m not using names.

Right around that time — late April — the architect happened to attend the Oakland edition of our Design Verification Testing seminar. She saw the presentation, and saw one of the design verification test chambers in action.

She realized design verification testing would be incredibly helpful in determining where and how the building envelope leaked.

The architect sent us a mock-up built by the contractor hired to repair the leaky house. The mock-up is a replica of how the current walls are assembled. It features everything the house has, from window to stucco cladding to building papers to electrical-box and air-conditioning penetrations.

She instructed us to test the mock-up for leaks in chamber conditions simulating 150-mph wind-driven rain.

Project Testing Director Courtney Murdock briefs yours truly on the mock-up we got from San Francisco for testing in the design verification test chamber.

Our Design Verification Testing Specialist Matt Travis, and Ron Tatley, BEI, who invented the Design Verification Test Chamber, plugged the mock-up into the chamber. They did a preliminary test at 25 mph wind-driven rain, which the mock-up immediately failed.

They knew it would, Ron said. That was the reason the mock up was here.

Ron and Matt fixed those first leaks. Then, with Project Testing Director Courtney Murdock recording the procedures and results, testing began in earnest. The tests used methodologies from ASTM tests including E 331, E 1105 and E 283, Ron said.

Yesterday, they looked for air leaks in the mock-up, found some and repaired them. This testing is different from what they do at most testing laboratories, Ron explained. At most labs your mock-up gets a pass or fail. That’s all you get, and what you do with that info is up to you.

In Design Verification Testing, you get a full report. It tells you whether your design passed or failed, but also where, when and how it failed, and exactly what you can do about it, based on what the testing revealed.

To be 100 percent useful and effective, Ron says, the Design Verification Testing should be incorporated into the planning stages of construction so that buildings are sound from the beginning. He said that could likely require the services of a qualified building-envelope consultant, as well as a design verification test chamber.

Some might balk at the price of a consultant and testing, Ron said, but both 10 times over are only a fraction of what you could pay for litigation and repair when water gets into walls that you guessed were good enough.

Like the job we’re testing now.

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